btrfs-progs: dump-tree: print invalid argument and strerror

Before this patch:

  $ ls nothingness
  ls: cannot access 'nothingness': No such file or directory
  $ btrfs inspect-internal dump-tree nothingness
  ERROR: not a block device or regular file: nothingness

The confusing error message makes users think that nonexistent file
exiss but is of a wrong type.

This patch lets check_arg_type return -errno if realpath failed.  And
print strerror if check_arg_type failed and the returned code is
negative. Like:

  $ btrfs inspect-internal dump-tree nothingness
  ERROR: invalid argument: nothingness: No such file or directory

Signed-off-by: Su Yue <suy.fnst@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>

0 files changed, 0 insertions, 0 deletions